1. Field of the Invention
The present invention relates generally to the field of rattle devices for generating sound, and more specifically to a rigid housing containing a cylindrical chamber closed by end members and containing a metal ball, for shaking back and forth along the chamber longitudinal axis so that the ball is guided to strike the end members perpendicularly for maximum impact and sound.
2. Description of the Prior Art
There have long been devices for generating various types of rattling sounds. One such device is the maraca, a percussion instrument consisting of a dried gourd containing loose pebbles for keeping rhythm in musical performances. Another is a whistle containing a ball which rattles with the air flow and trills the sound. Another is a child's toy rattler. In these and similar devices, the object is to create a particular quality rather than the maximum volume of sound. The moving projectile is typically light in weight, and thus causes a light impact on the interior walls of the device. The impact is further limited by the fact that the projectile strikes at a wide variety of random angles, often as only a glancing blow. As a result, only a fraction of the projectile's momentum is absorbed by the interior wall and converted into sound. A problem with such devices, if used for underwater signaling, is that the volume of sound generated is insufficient to signal a diver more than a few feet away.
An alternative is found in the underwater signaling device of Hart, U.S. Pat. No. 4,635,242, issued in 1987. Hart discloses a waterproof housing containing a switch-operated acoustic signal means, connected to a circuit driven by a power source. A problem with Hart is that it trades the simplicity and reliability of a manual rattling device for the unpredictability of electronics in a moist environment. In the event of an emergency, a leak in the housing may short out the circuitry or the switch may fail. Another problem is that Hart is comparatively expensive to manufacture and probably bulky.
It is thus an object of the present invention to provide an underwater signaling device which does not depend on numerous parts or electrical circuitry to function, and is thus reliable.
It is another object of the present invention to provide such a device which has the compactness and simplicity of a mechanical rattler.
It is still another object of the present invention to provide such a device which concentrates and maximizes the sound generating action of a mechanical rattler.
It is finally an object of the present invention to provide such a device which is durable and inexpensive to manufacture.